what is the nutritional perspective of the rumen complex

what is the purpose of fermentation?

• Fermentation transforms forage into the simple sugars that rumen microorganisms can use for growth

• Structural plant cell wall carbohydrates are broken down by the rumen microbes.

• simple sugars are converted into compounds used to support the rumen microbial population,

• sustains digestion and animal metabolism.

• Microbes ferment forages

• produce by-products called volatile fatty acids (VFA)

• VFA = major energy source for the ruminant animal (short chain fatty acids)

• a perfect symbiotic relationship between microbes and ruminants

herbivores can derive 70% of their energy intake from microbial breakdown - a classic example of mutualis

how does ruminant diet relate to one health

Not just ruminants/herbivores

Dietary polysaccharides that reach the human large intestine have a major impact on gut microbial ecology and health

why and how does diet affect the rumen?

first part of rumen=pre-ruminant/monogastric

Oesophageal Groove

• muscular structure

• lower end of the oesophagus

• closed, forms a tube allowing milk to go directly into the abomasum.

• prevents milk from being fermented or soured by the ruminal microorganisms.

• Sometimes called the reticular groove.

for milk digestion

bebby cows

“Young animals have the ability

to convert feed into growth

most efficiently during the first 2

months of their life,

• Growth rates will vary

according to

• the energy and protein

contents of the milk

• and the volume and

frequency with which it is

supplied “

what are calves fed first

colustrum

healthy rumen development increases productivity

milk replacer bags change as calve develops

Milk replacer-

• 5-6 litres of milk (13-15% of calf birth weight) daily, min two feeds,

• check correct lifestage

• read the label!!!

• digested in abomasum /bypasses the immature rumen

Then…

Concentrates from 3-4 days old

• ‘digested’ in rumen

• produces butyrate & propionate

• increases papillae number and

size

• improves rumen absorptive ability

• high energy, reduces gut fill

If fed alone (need fibre and feed) - so need better levels of concentrates

• causes hyperkeratinisation

• and clumping of papillae and

• decreased rumen motility

bottom pic show papillae - higher conc = better papillae development

another example of calf rumen development influenced by diet

• Concentrates are vital for rumen papillae development

Calves given the high-concentrate

diets had a significantly greater weight

of reticulo-rumen tissue at 12 weeks

• increase in the length and density

of papillae

• particularly in the anterior dorsal

and ventral sacs of the rumen, as

the intake of concentrates was

increased

• Compared to calves given the high-

roughage diets

• Marked relationship between the

performance of the animal and an

advanced stage of development of the

rumen papillae

creep/calf feed?

young calves have undeveloped rumens at birth

Need physiological changes before they can digest high fibre feeds

Digestion of milk and forages

• does not provide the end products needed to develop the rumen papillae

Concentrate feeds

• digested to propionic and butyric acids in the

rumen

• stimulate the growth of the rumen papillae.

Concentrate feeding for 3 to 4 weeks

• rumen not developed enough for fibre

fermentation

• rumen needs to be developed for calf to

digest substantial amounts of fibr

fibre or feed first?

healthy rumen development increass productivity

Feed

• Stimulates rumination and saliva

production

• Muscular development of rumen

• Increase pH

• Reduces keratinisation

• Reduces non nutritive oral behaviours

• Increase dry matter intake and size of

rumen

• Improves post weaning total dry matter

intake

• produces acetate

krebs cycle

correlation between VFAs. diet and rumen health

• Volatile fatty acids, = significant factors in the postnatal

development of the ruminal epithelium

• Practical importance

• size and length of ruminal papillae respond to

concentrations of VFA in the rumen.

• Animals on a high plane of nutrition, with abundant VFA

production

• = long, luxuriant papillae well suited to promote

absorption.

• Animals nutritionally deprived/poor diet

• = small, blunted papillae,

• require time on a high quality diet to allow for

development of their papillae and absorptive

capacity.

summarise conc vs forages

concentrations - start fermentation in rumen of calves- enzymes are different so digest more easily

structural carb = cellulose not starch

describe how calf → cow i.e. monogastric to ruminant

rumen grows in size and abomasum shrinks

weaning?

Transition period

• over 4 weeks –

• two weeks pre-weaning and two weeks post-weaning

Determined by solid feed intakes, (1kg concentrates)

• which reflects the rumen development,

Not just age or live-weight.

• need to be abale to maintain high intakes during weaning and prevent growth checks.

• Gradual weaning, where liquid feed is reduced over time in volume and frequency

of feeds,

• stimulates solid feed intake preferable to abrupt weaning

how do we wean calves?

Bucket rearing system

• Reduce milk and frequency of feeds

• seven to 14 days up to weaning.

• increase of solid feed intake,

• improve the efficiency of gain

• maximize the economic performance of the calf.

Automated feeders

• Automatic feeders reduce the daily

volume of milk on offer over a pre-defined

period up to weaning.

• gradual weaning process with minimal

labor input and results in a smoother

transition for the calf.

• Careful re slow eating individuals

how do we time the feeding for growing calves?

quantity involved in weaning and how

dont need to know numbers

what exactly happens in rumen?

Bacteria ferment fibre - cellulose/pectins,glucans

• Fibre digested by bacteria and used to grow

• By products of fermentation released

into rumen

• Volatile fatty acids (VFAs) are rumen byproducts from CHO digestion

• Called short chain fatty acids (SFAs) in human and pet nutrition

• VFAs are organic fatty acids with 1 to

6 carbons

how do Plant CHOs used as energy source by cellulolytic bacteria to grow

what happens to plant CHOs?

Volatile fatty acids diffuse out of rumen into blood,

must be continuously removed or pH drops

6-8kg VFAs produced/24hrs-

• main energy source for the ruminant

70-80% absorbed from reticulorumen

14-18% absorbed from omasum

• Mostly by simple diffusion

• Some facilitated diffusion in exchange

for HCO3- which is a buffer and stops

rumen getting acid

• Transported to liver for processing

Loses 3-11% of the fermented energy as methane

how are VFAs absorbed?

• diffusion through the epithelium, down a

concentration gradient

• undergo different degrees of metabolism

Acetic acid passes through the

epithelium largely unchanged

• oxidised throughout most of

the body to generate ATP.

• utilised minimally in the liver,

• major source of acetyl CoA

for synthesis of lipids

Propionic acid passes through the

epithelium largely unchanged

• almost completely removed from

portal blood by the liver.

within liver, propionate serves

as a major substrate for

gluconeogenesis,

critical to the ruminant because

almost no glucose reaches the

small intestine for absorption

Butyric acid, metabolised in the epithelium

•to beta-hydroxybutyric acid (ketone body)

•is oxidised in many tissues for energy productio

how is protein degraded in the rumen?

• Bacteria break down food and fibre

protein into amino acids-

• Bacteria absorb and use some amino

acids to grow and live

Bacterial byproducts of protein digestion

are

•Ammonia

•VFAs

• Micro-organisms mostly use these to

make more amino acids

• The bacteria pass out of the rumen and

are absorbed in the small intestine

• The cow uses/digests the microbial

protein

how is plant protein used by microorganisms to grow?

what is degradable vs undegradable protein?

sometimes we need to protect some of the nutrients in the rumen so bacteria csnt ferment them so we give undegradable protein

Rumen degradable protein (RDP)

• Feeds the rumen bacteria

• Ensures an adequate supply of microbial

protein

• Microbial protein is the highest quality protein

available

Undegradable protein (RUDP)

• Rumen undegradable protein passes through

the rumen unchanged

• Digested in the small intestin

are fats good for cows?

no - it coats the bacteria and kills them

Conveniently, most plants are low in fat (and low in

energy)

Unsaturated fats are toxic to

cellulolytic bacteria – stops

fermentation

•Bacteria hydrogenate to

saturated fats (uses up H2

reduces acidity

•Can convert to non-toxic fatty

acids e.g. conjugated linoleic

acid (CLA)

Manufacturers provide protected fats

which bypass the rumen

• Free fatty acids(85-90%) &

bacteria pass into SI -

• the phospholipds in their cell

membranes are absorbed in the

small intestine

how do microorganisms use plant fats?

summarise this presentation